The University of Miami proposals to participate in the NIH sponsored MDRD study to compare and investigate the efficacy of a low protein diet and phosphorus restriction, a very low protein diet with dietary supplement and phosphorus restriction and a diet with moderate protein intake and phosphorus restriction on the course of progressive chronic renal insufficiency. A team of physicians and paramedical personnel experienced in the longterm care of patients with renal disease is committed to an effective conduct of the Study with Institutional support. An administrative center within the Division of Nephrology will be used exclusively by the MDRD team. An outpatient clinic center will share specifically identified space with another clinical research team in an area immediately adjacent to a general inpatient and outpatient Clinical Research Center. Laboratory, pharmacy and radiopharmacy support will be provided by the University of Miami Hospitals and Clinics. About 75 potentially eligible patients have been identified on clinical grounds from several sources which include the Renal Clinic and the General Medicine Clinic at the University of Miami/Jackson Memorial Medical Center, the Renal Clinic at the Miami Veterans Administration Medical Center and patients from individual nephrologists within and outside the Medical Center. Support by the major nephrology groups within the greater Miami area, Dade County and Broward County has been committed. Presentations to enlarge Dade County Medical Association, local HMO's and family practice groups and advertisement through the local chapters of the National Kidney Foundation are planned to enlarge the base for recruitment of patients. In addition to the usual population of patients with chronic progressive renal insufficiency existing throughout the continental United States, the special geographical location of Miami with its subtropical climate makes available for the Study a unique population of retired, upper and middle class, patients. The population available and the interest in the Study by patients and physicians alike indicate that 50 to 60 selected volunteer patients with chronic progressive renal insufficiency can be entered, randomized and followed in Miami using protocols set by NIH, and in cooperation with other MDRD Clinical Centers, the MDRD ta Coordinating Center and NIDDK Staff.